Intracellularly transported adenosine induces MCF-7 human breast cancer cells by accumulating AMID in the nucleus

Extracellular adenosine induced apoptosis of MCF-7 human breast cancer cells in a concentration (10 μM-10 mM)- and treatment time (24-72 h)-dependent manner, and the effect was inhibited by the adenosine transporter inhibitor dipyridamole, but not an inhibitor of adenosine kinase, an inhibitor of AMP-activated protein kinase, or inhibitors for A1, A2a, A2b, and A3 adenosine receptors. No significant activation of caspase-7, -8, or -9 was obtained with adenosine. Adenosine promoted translocation of apoptosis-inducing factor (AIF)-homologous mitochondrion-associated inducer of death (AMID) from the cytosol into the nucleus, although the total amount of AMID was not affected. Adenosine-induced MCF-7 cell death was abrogated by knocking-down AMID. The results of the present study indicate that intracellularly transported adenosine induces MCF-7 cell apoptosis by accumulating AMID in the nucleus in a caspase-independent manner.